"I could definitely write an eighth, ninth, tenth," Rowling, 45, told the TV talk queen during a satellite interview. "I'm not going to say I won't. I don't think I will … I feel I am done, but you never know."

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Not that she's completely put down her pen. Rowling plans to write more books, and feels there is no need to match or top her previous achievement.

"I did it. I'm really proud I did it," she said. "But this is a new phase."

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The old phase was pretty good to Rowling, who still remembers being a broke single mom. After selling more than 400 million books and launching a series celebrated on screen and in a theme park in Florida, Rowling is a billionaire.

She said her biggest regret is that her mother, who died before the first book was even finished, much less published, never saw her success.